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Add loop_invariants for some Int power functions #327

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Add loop_invariants for some Int power functions #327

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41e32cb
add invariants
thanhnguyen-aws Apr 17, 2025
9c9d863
Merge branch 'main' into addvariant
tautschnig Apr 23, 2025
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3 changes: 3 additions & 0 deletions library/core/src/num/int_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1589,6 +1589,7 @@ macro_rules! int_impl {
let mut base = self;
let mut acc: Self = 1;

#[safety::loop_invariant(true)]
loop {
if (exp & 1) == 1 {
acc = try_opt!(acc.checked_mul(base));
Expand Down Expand Up @@ -2299,6 +2300,7 @@ macro_rules! int_impl {
let mut acc: Self = 1;

if intrinsics::is_val_statically_known(exp) {
#[safety::loop_invariant(exp>=1)]
while exp > 1 {
if (exp & 1) == 1 {
acc = acc.wrapping_mul(base);
Expand All @@ -2316,6 +2318,7 @@ macro_rules! int_impl {
// at compile time. We can't use the same code for the constant
// exponent case because LLVM is currently unable to unroll
// this loop.
#[safety::loop_invariant(true)]
loop {
if (exp & 1) == 1 {
acc = acc.wrapping_mul(base);
Expand Down
4 changes: 4 additions & 0 deletions library/core/src/num/uint_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1780,6 +1780,7 @@ macro_rules! uint_impl {
let mut base = self;
let mut acc: Self = 1;

#[safety::loop_invariant(true)]
loop {
if (exp & 1) == 1 {
acc = try_opt!(acc.checked_mul(base));
Expand Down Expand Up @@ -2349,6 +2350,7 @@ macro_rules! uint_impl {
let mut acc: Self = 1;

if intrinsics::is_val_statically_known(exp) {
#[safety::loop_invariant(exp>=1)]
while exp > 1 {
if (exp & 1) == 1 {
acc = acc.wrapping_mul(base);
Expand All @@ -2366,6 +2368,7 @@ macro_rules! uint_impl {
// at compile time. We can't use the same code for the constant
// exponent case because LLVM is currently unable to unroll
// this loop.
#[safety::loop_invariant(true)]
loop {
if (exp & 1) == 1 {
acc = acc.wrapping_mul(base);
Expand Down Expand Up @@ -3044,6 +3047,7 @@ macro_rules! uint_impl {
// Scratch space for storing results of overflowing_mul.
let mut r;

#[safety::loop_invariant(true)]
loop {
if (exp & 1) == 1 {
r = acc.overflowing_mul(base);
Expand Down
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